The invention relates to a cutting tool the edge of which is coated with layers of titanium carbide, titanium carbonitride and/or titanium nitride.
It is known that cutting tools, in particular those of hard metal, can be provided with coatings of titanium carbide, titanium carbonitride and/or titanium nitride and the wear-resistance of these tools can thereby be improved considerably. The use of binder-metal-free hard substance coatings of nitrides and carbonitrides of elements of columns IVa to VIa of the periodic table for abrasion protection of tools of hard metals is described, for example in FRG Patent No. 1 959 690, and among the aforementioned group of hard materials, hard materials based on the element titanium have proved themselves particularly well in practice.
A further increase in the life of cutting tools made of hard metals can be attained in accordance with the proposal in FRG Patent No. 2 263 210 by providing a multi-layer coating of titanium carbide, titanium carbonitride and titanium nitride. Indexable inserts of hard metals having a coating composed of several layers of titanium carbide, titanium carbonitride and titanium nitride are particularly well suited to machining of steels at medium cutting speeds.
Higher cutting speeds, however, generate high temperatures at the noses of the cutting tools, resulting in a rapidly progressing diffusion and oxidation wear. Accordingly, it has already been proposed for this application to increase the service life of such cutting tools by applying thin layers of aluminum oxide to them. In the present state of the art, for medium cutting speeds and large chip cross sections, cutting inserts coated with titanium carbide, titanium carbonitride and titanium nitride have become established; for high cutting speeds, coatings of oxides of aluminum or zirconium, often also in combination with a coating with the nitrides and carbides of titanium, are preferably used.